The brain chooses fats or carbohydrates for meals by itself

Scientists have found that when glucose is deficient in the body (a condition called glucoprivia), the brain activates special circuits of neurons in the paraventricular nucleus of the hypothalamus (PVH), an area responsible for regulating nutrition and metabolism. For the experiment, mice were injected with 2-deoxy-D-glucose (2DG), a substance that temporarily blocks the use of glucose by cells.

After that, the animals began to consume both high-carbohydrate (HCD) and high-fat (HFD) foods more actively. But, as the analysis showed, these two types of appetite were controlled by different neural circuits.:

• neurons regulated by AMP kinase and releasing corticotropin-releasing hormone (CRH) were responsible for the desire to eat something sweet or rich in carbohydrates;
• and the desire for fatty foods was controlled by neurons with melanocortin-4 (MC4R) receptors.

In addition, the researchers found that neurons that produce neuropeptide Y (NPY), one of the main appetite stimulants, play a key role in this process. These neurons, located in the nucleus of the solitary pathway (NTS) and the ventrolateral medulla oblongata (VLM), activate both groups of cells in the PVH, increasing the desire to eat both fatty and sweet foods.

However, another group of NPY neurons, already in the arcuate nucleus of the hypothalamus (ARC), acts differently: it inhibits MC4R neurons, which leads to increased consumption of fatty foods, but not carbohydrates.

The results showed for the first time that the brain controls cravings for fats and carbohydrates differently, using two independent systems. This discovery may explain why people react differently to a lack of energy: some are drawn to sweets, while others are drawn to fatty foods.

The study highlights that our food choices are not just a matter of will, but the result of a complex brain working to restore energy balance in different ways.